Abstract
Recently, the application and development of flexible microwave-absorption composites based on silicone rubber have gradually become a research hot spot. In this study, methyl vinyl phenyl silicone rubber (MPVQ)/carbonyl iron particles (CIPs)/graphene (GR) composites were prepared by mechanical blending, and the effects of thermal-ageing temperature on the microwave-absorption properties of the composites were investigated. The mechanism of the thermal-ageing temperature’s effects on microwave-absorption behaviour was identified. The results show that unaged composites have superior microwave-absorption properties, with a minimum reflection loss (RLmin) of − 87.73 dB, a lowest thickness of 1.46 mm, and an effective absorption bandwidth (EAB, RL < − 10 dB) reaching 5.8 GHz (9.9–15.7 GHz). With ageing at 240 °C for 24 h, the RLmin at a frequency of 5.48 GHz is − 45.55 dB with a thickness of 2.55 mm, and the EAB value reaches 2 GHz (range 4.6–6.6 GHz). In the thermal-ageing process, a crosslinking reaction occurs in MPVQ with an increase in crosslinking density from 5.88 × 10−5 mol g−1 (unaged) to 4.69 × 10−4 mol g−1 (aged at 240 °C). Simultaneously, thermal degradation of the composites leads to a reduction in the rubber concentration. In addition, a small amount of CIPs are oxidized to Fe3O4, and the remaining CIPs aggregate to generate more electrically conductive pathways. Consequently, the dielectric loss of the composites will be significantly improved, resulting in poor impedance matching. The microwave-absorption properties of the composites gradually decrease with increasing thermal-ageing temperature from 200 to 240 °C.
Highlights
To prepare high-performance rubber-based absorbing materials, some wave-absorbing fillers are essential in the rubber matrix, such as dielectric materials and magnetic materials, including carbonyl iron particles (CIPs), FeSiAl, ferrite and so on[11–13]
CIP/polyurethane (PU)/graphene (GR) composites were manufactured by Duan et al.[15], who demonstrated that the synergistic effects of dielectric/
After ageing at 200 °C for 12 days, the RLmin of the composites changed from − 33.7 to − 18.8 dB, and the effective absorption bandwidth (EAB) decreased from 1.76 to 1.02 GHz, indicating that the thermal-ageing resistance of silicone rubber as the matrix needs to be further improved, while using only CIPs as microwave absorbers has disadvantages in balancing the complex relative permittivity and permeability
Summary
With the prosperous development of the electronic communication industry, the issue of electromagnetic wave pollution has become increasingly serious, which is harmful to human health, information safety and the ecological environment[1–5]. Zhang et al.[17] reported the effect of thermal-ageing time on the microwave-absorption properties of CIP/VMQ composites.
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